Pulse grounded search fabricates legislative characterizations that contradict the cited source article. Observed 2026-07-11 pm prod: the grounded text (Gemini synthesis) stated '7 years: The time limit within which these institutional investors must sell their existing single-family homes' and 'By forcing institutional investors to sell off single-family homes within seven years'. The cited CBS News article actually says 'limiting institutional investors from purchasing certain single-family homes' — the opposite action (purchase ban, not forced sale). The 7-year sell requirement only applies to narrow build-to-rent/renovate-to-rent exceptions per the actual law (21st Century ROAD to Housing Act), confirmed by CNBC and Morgan Lewis legal analysis. The writer faithfully used the grounded text's source_quote (byte span [1598, 1823]), so the error is upstream in Gemini's synthesis, not the writer. Attribution method was 'keyword' (not quote_anchor), so no content verification was performed against the actual CBS article. This is distinct from figure fabrication — the grounded text fabricates the characterization of a law's mechanism (sell vs purchase ban) rather than a specific number.
Add a post-attribution characterization verification step: after matching a story to a source URL via keyword/quote_anchor, cross-check that the grounded text's key claims (especially legislative/policy characterizations like 'forces to sell' vs 'limits purchases') are corroborated by the actual source article content. The existing source_quote + quote_span machinery verifies figures (figure_ok); extending it to verify action-characterizations would catch this class of error. Specifically: when the grounded text attributes a specific action to a law/policy (forces/bans/requires/limits), verify the source article uses a semantically compatible verb. This could be a lightweight LLM call comparing the grounded claim against the article's actual text, or a keyword-based heuristic (does the article contain 'sell'/'divest' or 'purchase'/'buy'?).